1. Field of the Invention
The present invention relates to a thermal transfer image-receiving sheet which can receive a colorant transferred from a thermal transfer sheet upon heating. More particularly, the present invention relates to a thermal transfer image-receiving sheet which can yield sublimation transferred images on a receptive layer having excellent (improved) resistance to hand cream, resistance to sebum, particularly sebum of human's nose, cheek, and forehead portions, resistance to plasticizers, and resistance to fats and oils.
2. Prior Art
In recent years, a system, wherein video photographed images, television images, and static images such as computer graphics are directly printed in a full color form, has been advanced, and the market of this system has been rapidly expanded. Among others, attention has been drawn to a system wherein a sublimable dye is provided as a recording material and is put on top of an image-receiving sheet and the assembly is heated by means of a thermal head in response to a recording signal to transfer the dye onto the image-receiving sheet, whereby a recorded image is formed. In this recording system, since the colorant is a dye which is very vivid and highly transparent, the formed images have excellent reproduction of intermediate colors and gradation and have the same quality as images formed by conventional full-color offset printing and gravure printing and have high quality comparable with photographic images. Further, the provision of a protective layer by thermal transfer on the receptive layer with a dye image formed thereon has been extensively adopted for enhancing fastness or resistance properties of thermally transferred prints, such as abrasion resistance and lightfastness.
The sublimation transferred images have excellent durability (fastness or resistance properties), but on the other hand, suffer from the following drawbacks. Specifically, when the image formed face is in contact, for example, with hand cream (a material containing a humectant/rough skin preventive component, such as commercially available Mentholatum (trademark)) or sebum, particularly sebum of human's nose, cheek, and forehead portions, for a long period of time, the fat-and-oil component contained in them penetrates through the surface of the protective layer and reaches the receptive layer or the intermediate layer. In this case, when distortion caused by heating at the time of printing exists in the intermediate layer, the distortion is released and cracking occurs in the intermediate layer, as well as in the overlying receptive layer and protective layer. In particular, when the protective layer exists, fine cracks are formed in the printed face, disadvantageously resulting in significantly deteriorated image quality.
Further, when the image formed face is in contact with a plasticizer or a plasticizer-containing material, for example, when the images are stored in a soft vinyl chloride resin file, when the images are in contact with a plastic eraser or the like for a long period of time, or when fats and oils, such as machine oils or castor oils, are in the state of deposition on the images for a long period of time, as with the above case, the plasticizer component or the fat-and-oil component penetrates through the surface of the protective layer and this causes fine cracking in the printed face, disadvantageously resulting in significantly deteriorated image quality.
For example, the use of a flexible resin or a highly soft resin in the intermediate layer or receptive layer has hitherto been made as a measure for preventing cracking. In this method, however, when the print is stored for a long period of time, for example, blurring of pixels of the image disadvantageously occurs. Further, when a highly flexible or soft resin in the protective layer is used, for some printing conditions in the transfer of the protective layer, poor transferability of the resin poses problems including that the appearance of the print is deteriorated and broken pieces of the resin are left as refuse in the printer, leading to a transfer failure in the preparation of a next print.